1. Field of Endeavor
The present invention relates to an X-ray source and more particularly to a femtosecond laser-electron X-ray source.
2. State of Technology
U.S. Pat. No. 6,035,015 for a Compton backscattered collmated X-ray source by Ronald D. Ruth, and Zhirong Huang, issued Mar. 7, 2000, and assigned to The Board of Trustees of the Leland Stanford Junior University provides the following description: xe2x80x9cIn the past two decades x-ray lithography (XRL) has been developed as an alternative to optical lithography as feature sizes of silicon chips continue to shrink according to the Moore""s law (S.P.I.E. Symp. Proceedings xe2x80x9cElectron Beam, X-ray, and Ion-Beam Submicrometer Lithographies for Manufacturing,xe2x80x9d 1990-1996). Today, optical lithography is reaching some fundamental limits, and x-ray lithography is emerging as the primary successor technology needed for future lithography development. The two biggest challenges facing x-ray lithography are perhaps the fabrication of x-ray masks and the development of the x-ray sources. While the technology of mask patterning is evolving by means of electron beam lithography and advances in material science, economical exposure sources are still lacking. At present there are three types of x-ray sources that could provide sufficient flux for a reasonable exposure time (S.P.I.E. Symp. Proceedings xe2x80x9cElectron Beam, X-ray, and Ion-Beam Submicrometer Lithographies for Manufacturing,xe2x80x9d 1990-1996): synchrotrons, plasma-based sources, and transition radiation (TR) sources. Among these, plasma-based sources are relatively easy to obtain but have the lowest available x-ray power level and no collimation. TR sources employ moderate energy electron linacs (25 MeV to 250 MeV) to bombard a stack of thin Beryllium (Be) foils. The resulting x-ray beam is well collimated but hollow in the forward direction. Special methods of making the cross section of the x-ray beam uniform and eliminating the background radiation are needed. Synchrotrons, on the other hand, are the preferred sources because they are powerful and stable. However, in order to generate x-rays having the optimal wavelength for XRL (around 1 nm), synchrotrons operate with high-energy electron beams (around 1 GeV when using conventional magnets and even 600 MeV when using superconducting dipoles). Hence the entire system (synchrotron, injector and radiation shielding) can be very expensive and complex. In addition, special beam lenses and steppers are necessary to facilitate wafer production, which translates to a huge initial investment for manufacturers. There are a number of sources of x-rays which depend upon Compton scattering. Compton scattering is a phenomenon of elastic scattering of photons and electrons. Since both the total energy and the momentum are conserved during the process, scattered photons with much higher energy (light with much shorter wavelength) can be obtained in this way. A laser beam collides nearly head-on with and is scattered off a high energy electron beam in order to generate x-rays (or even gamma-rays) for various applications.xe2x80x9d
Features and advantages of the present invention will become apparent from the following description. Applicants are providing this description, which includes drawings and examples of specific embodiments, to give a broad representation of the invention. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this description and by practice of the invention. The scope of the invention is not intended to be limited to the particular forms disclosed and the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
The present invention provides a femtosecond laser-electron X-ray source. A high-brightness relativistic electron injector produces an electron beam pulse train. A system accelerates the electron beam pulse train. The femtosecond laser-electron X-ray source includes a high intra-cavity power, mode-locked laser and an x-ray optics system. In one embodiment the system for accelerating the electron beam pulse train includes a compact electron ring with an rf cavity. In another embodiment the system for accelerating the electron beam pulse train is a superconducting linac.
The invention is susceptible to modifications and alternative forms. Specific embodiments are shown by way of example. It is to be understood that the invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.